In recent years there has been increasing use of endoscopes for minimally invasive treatment and diagnosis. For example, endoscopes are often used in diagnostic procedures in an attempt to visualize and diagnose problems in the sinus structures, as well as in sinus surgeries. Due to its proximity to sensitive orbital and cerebral structures, access, visualization, and surgeon confidence all factor into clinical efficacy, patient safety and minimizing complications in diagnosing and performing surgery in this challenging anatomical area. However, current endoscopes, and related instrumentation do not provide the flexibility, dexterity and small enough diameter to access, directly visualize, and effectively perform sensitive procedures throughout all sinus structures.
Chronic sinusitis affects approximately 33 million Americans each year, and has become one of the most prevalent chronic diseases. See Bajracharva H, Hinthorn D. “Sinusitis, Chronic” www.emedicine.com/med/topic2556.htm. Chronic sinusitis is generally characterized as sinusitis lasting longer than 3 months despite treatment, and/or four recurrences of acute sinusitis. The prevalence of chronic sinusitis is likely to grow with increasing pollution, urban sprawl and resistance to antibiotics. See id.
Because of its persistent nature, chronic sinusitis has become a significant cause of morbidity and involves considerable expense to the worldwide health care system. Chronic sinusitis results in 18 to 22 million U.S. physician office visits annually (See “Adult Chronic Rhinosinusitis: Definitions, Diagnosis, Epidemiology, and Pathophysiology,” Otolaryngology—Head & Neck Surgery, Supplement, (2003) September: 129: S1-84), and, in 2001, resulted in 1.3 million documented visits to hospital outpatient facilities. See National Hospital Ambulatory Medical Care Survey: 2001 Outpatient Department Summary. It was the most frequently reported chronic disease in the 1993 National Health Interview Survey, affecting 14.7% of the population and was the fifth most common use of antibiotics. See Sinusitis, American Academy of Allergy, Asthma and Immunology, www.aaaai.org/patients/resources/fastfacts/sinusitis.stm. In 2002, Sinusitis accounted for 9% of all pediatric and 21% of all adult antibiotic prescriptions and, thus, contributes to the increasing rate of antibiotic resistance. See “Antimicrobial Treatment Guidelines for Acute Bacterial Rhinosinusitis,” Otolaryngology—Head & Neck Surgery Supplement (2004) January; 130: 1-49. Untreated sinusitis affects personal productivity and quality of life. It is associated with exacerbation of asthma and serious complications, such as brain abscess and meningitis, which can produce significant morbidity and mortality. See Bajracharva H, Hinthorn D. “Sinusitis, Chronic” www.emedicine.com/med/topic2556.htm. While some individuals can be successfully treated with medications, others require surgery.
Millions of diagnostic procedures are conducted each year to attempt to visualize and diagnose problems in the sinus structures. In 2001, approximately 200,000 sinus surgeries were performed in the U.S. See id. The surgeries were performed to treat chronic sinusitis, as well as for excision of tumors and polyps, cerebrospinal fluid (CSF) leak closure, orbital and optic nerve decompression, dacryocystorhinostomy, choanal atresia repair, foreign body removal and epistaxis repair. See Patel A, Vartanian J, Guzman Portugal L. “Functional Endoscopic Sinus Surgery” www.emedicine.com/ent/topic758.htm. The difficulty visualizing and accessing certain areas of the sinus structures, particularly the frontal and the ethmoid sinuses, the proximity of the sinus to sensitive structures, such as the orbit and neurovascular structures, and the presence of abnormal growths or anatomy can cause sinus surgery to be challenging, time consuming, and subject to serious complications. Complications can include: orbital injury or hematoma; bleeding; infection; synechiae formation; CSF leaks; direct brain injury; denuded bone resulting in delayed healing; and diplopia. See Patel A, Vartanian J, Guzman Portugal L. “Functional Endoscopic Sinus Surgery” www.emedicine.com/ent/topic758.htm; Rombout J, deVries N. “Complication in Sinus Surgery and new Classification Proposal.” American Journal of Rhinology (2001) 25:280-286; Kennedy D. “Functional Endoscopic Sinus Surgery: Concepts, Surgical Indications, and Instrumentation,” Diseases of the Sinuses, Elsevier, 2000, pp. 197-210.
While the incidence of major complications during sinus surgery is low (see Rombout J, deVries N. “Complication in Sinus Surgery and new Classification Proposal.” American Journal of Rhinology (2001) 25:280-286), complications such as orbital damage and CSF leaks can cause significant morbidity when they do occur. See Rene C, Rose G, Letnall R, Moseley I. “Major orbital complications of endoscopic sinus surgery” British Journal of Ophthalmology (2001) May 85:598-603. In surgically challenging frontal sinusotomy procedures, damaging exploration or inadvertent stripping of mucosa can result in prolonged morbidity and multiple surgical procedures. See Kennedy D. “Functional Endoscopic Sinus Surgery: Concepts, Surgical Indications, and Instrumentation,” Diseases of the Sinuses, Elsevier, 2000, pp. 197-210.
The second largest cause of failure in endoscopic maxillary sinus surgery identified in Richtsmeier's study was ethmoid/frontal disease that couldn't be visualized on a CT scan. See Richtsmeier W J. “Top 10 Reasons for Endoscopic Maxillary Sinus Surgery Failure,” Laryngoscope (2001) November 111:1952-6. Other studies have highlighted the role of incomplete ethmoid dissection and post-operative scarring in the frontal and ethmoid sinuses as important factors in surgical failure. See Ramadan H. “Surgical Causes of Failure in Endoscopic Sinus Surgery,” Laryngoscope 1999; 109:27-9; Shah, N. “Functional Endoscopic Sinus Surgery,” www.bhj.org/journal/1999—4104-Oct99/SP—659.HTM. Direct access, clear visualization, and surgeon confidence can all affect outcomes. As such, improved endoscopes are needed that would be smaller, more dextrous, more flexible and allow the physician greater access, visualization and the ability to perform procedures in all of the sinus structures.
Bronchoscopy using endoscopes is also a proven method of directly visualizing the airways of the lung and sampling suspicious tissue. However, current diameters of endoscopes (e.g., ranging from 2.2 mm ultra thin visualization only scopes up to 6.2 mm) prevents access and use in over half the area of the lung. While other forms of testing have evolved (laser induced fluorescence endoscope (LIFE) airway imaging, endobronchial ultrasound, virtual bronchoscopy, spiral CT, CT with nodule enhancement and PET scan), none of the methods offer the unique and significant advantages of conventional bronchoscopy, i.e., direct visualization for accurate location, and collection of tissue samples with minimal safety concerns.
In the United States, the new, diagnosed cases of cancer of the lung and bronchus were estimated at approximately 174,000 in 2003. See Jemal A, Tiwari R, Murray T, et al. Cancer statistics, 2004. CA Cancer J Clin (2004) 54: 8-29. U.S. populations of current and ex-smokers (50 million each) make it probable that this significant health problem will continue. See American Cancer Society. (1999) Cancer Facts and Figures, 1999. American Cancer Society Atlanta, Ga.
Lung cancer is the most common cause of cancer deaths in the U.S., accounting for more deaths in 2000 than from prostate, breast, and colorectal cancer combined. Less than 15% of patients survive 5 years after diagnosis. The poor prognosis is largely attributable to the lack of effective early detection methods and the inability to cure metastatic disease. Early diagnosis and treatment of lung cancer can significantly improve the patient's chances of survival. See Naruke, T, Tsuchiya, R, Kondo, H, et al (1997) Implications of staging in lung cancer. Chest 112(suppl) 4, 242S-248S; Mountain, C F, Dresler, C M (1997) Regional lymph node classification for lung cancer staging. Chest 111, 1718-1723. Patients with the most favorable clinical stage, IA disease, have a 5-year survival of about 60%, while those with more advanced disease, clinical stage II-IV, have 5-year survival rates ranging from 40% to less than 5%.
Clearly, early identification and intervention are key to improving cure rates. Currently, however, over two-thirds of the patients diagnosed have regional lymph-node involvement or distant disease at diagnosis. See Ihde D. C. Chemotherapy of lung cancer, N. Engl. J. Med., 327: 1434-1441, 1992. The solution requires a shift in the therapeutic paradigm from targeting advanced clinically manifest lung cancer to identifying asymptomatic, preinvasive and early-invasive lesions, coupled with accurate diagnosis and staging.
Bronchoscopy is one of the most commonly used diagnostic and therapeutic procedures in pulmonology, and is routinely used to screen a subgroup of patients at high risk for lung cancer, including those with a) risk factors (emphysema, family history, environmental exposures), b) atypical sputum cytology, or c) suspicious chest x-ray. These procedures are well-tolerated by most patients using local anesthesia and conscious sedation, with exam times of 20-45 minutes, which refined techniques can extend to 60-120 minutes without compromising patient comfort. Direct visualization of the airways can localize potential abnormalities of the tracheobronchial mucosa. The characteristics of these abnormalities (color, stiffness, vascularization, smooth margins, etc.) help to establish the diagnosis and direct treatment. The channels of the flexible bronchoscope support the removal of secretions and samples through bronchial washing, brushing, and biopsy to establish histologic diagnosis, with an average diagnostic yield of 90% for central lung cancers. See Mazzone, P., Jain, P., Arroliga, A. C., Matthay, R. A., Bronchoscopy and Needle Biopsy Techniques for Diagnosis and Staging of Lung Cancer. Clinics in Chest Medicine. 23:137-158, 2002; C. Agusti, A. Xaubet, “Bronchoscopic procedures in the new millennium” www.personal.u-net.com/˜ersj/Buyers %20Guide %20for %20the %20Internet/agusti37-38.html.htm.
The current size (diameter) of conventional bronchoscopes have limited the ability to access the majority of the lung. Reductions in the size of the developmental bronchoscope have demonstrated success in expanding its reach and capabilities. See Schoenfeld, N., et. al., Ultrathin Bronchoscopy as a New Tool in the Diagnosis of Peripheral Lung Lesions, Lung Cancer Frontiers, No. 9, October 2000; Rooney, C. P., Wolf, K., McLennan, G. Ultrathin Bronchoscopy as an Adjunct to Standard Bronchoscopy in the Diagnosis of Peripheral Lung Lesions, Respiration, 69:1, 2002.
Although desirable, it is currently impractical to use bronchoscopy to screen the general population or to examine small bronchioles. However, since bronchoscopy is currently part of a routine protocol for high risk populations, it would be desirable to expand access into the bronchial tree to more areas where lung cancer predominates, such as the upper lobes, or to targeted areas identified by CT. See Byers T E, Vena J E, Rzepka T F. “Predilection of Lung Cancer for the Upper Lobes: An Epidemiologic Inquiry,” J Natl Cancer Inst. 1984 June; 72(6): 1271-5. Thus, additional improvements in bronchoscopes are needed.
Some recent efforts have focused on developing endoscopes with active catheters in which a shape memory alloy (SMA) that is deformable when electrically heated is utilized as actuator elements. For example, JP Laid-Open publication No. H11-48171 published Feb. 23, 1999 proposes an active catheter of an outer skeleton type in which a liner coil is disposed outside of a plurality of coiled actuators which are made of a shape memory alloy. The SMA actuators are directly electrically energized to permit the active catheter to be bent or flexed. U.S. Pat. No. 6,672,338 also discloses an active catheter having a linear coil forming an elastically deformable skeletal structure and a coil spring actuator made of shape memory alloy. However, improvements in endoscope design and actuation are still needed.